1. Field of the Invention
The present invention relates to a silicon oxide layer having a top surface in the shape of plural hills, wherein more particularly, the plural hills can be table-shaped or breast-shaped.
2. Description of the Prior Art
High voltage devices integrated with low voltage logic circuits are finding applications in a diverse range of office and telecommunications terminal products, particularly when combined with advances in display technology.
In order to avoid device breakdown due to generation of a very high electric field within the device, the high voltage MOS devices maybe fabricated using a planar field effect transistors (FET) with thick oxide, or with N or P channel drain-extended metal-oxide-semiconductor (DEMOS) transistor devices, such as lateral diffused MOS (LDMOS) devices.
When constrained by the gate oxide processes in use today, there are significant processing challenges to having gate oxides on the same die that can support both high voltage devices and low voltage devices operating at different voltages. A gate oxide layer on a particular die is typically optimized for either the high voltage device or the low voltage device, but not for both at the same time. Therefore, either the high voltage device or the low voltage device will not reach their original performance due to the unsuitable gate oxide layer.